Cars House

i took my 1997 5-series to autozone, where they can diagnose the obd codes for free. when checked, the check engine code that my car showed was p0420-catalyst system effieciency below threshold (bank 1). any idea what this may be? i figured it may be one of the oxygen sensors but i wanted to get a second opinion. does anyone have the obd codes available for future use??
thanks
art

Your catalytic converter is probably gunked up. I would change the O2 sensors you should have 2 or 4. O2 sensors should be changed every 60-70K. What's your mileage?

You can try one thing first. Get a tank of Mobil 93 octane, add some Techron cleaner and go drive the car like you just stole it to go by crack.
"Blowing out the Cats" with some good detergent gas for an hour might get you back over the threshold. Basically your trying to burn the soot off the platinum honeycomb in the Catalytic Converter and on the O2 sensors with increased exhaust gas temps.

Read this, it's for a Mercury but it all boils down to the same O2 sensor cat problem
http://www.alldata.com/techtips/2003/20031110a.html

Unplug the battery and reconnect it after the drive and see if the code is still there.

i just passed 106000 miles so i'm leaning towards a faulty O2 sensor. . .is there any way to accurately test each sensor to see if they are causing a problem? thanks